Exploring the dynamic nature of OCP crystals by combined use of diffraction and in crystallo spectrophotometry at room-temperature.

The photoactive Orange Carotenoid Protein (OCP) is a reversible photoswitch which serves photoprotection in cyanobacteria (Wilson et al. 2006). OCP is functionalized by a keto-carotenoid pigment which, in the presence of a blue-green photon, is able to induce conformational changes resulting in a photoactivated state capable of quenching an excess of absorbed light energy. Preliminary experiments offered first evidence that dehydration of OCP crystals lead to the trapping of a pre-activated state. The very goal of our experiment is to verify this hypothesis by simultaneous collection of diffraction and spectroscopic data from crystals at room-temperature and at varied levels of humidity.

光活性橙色素蛋白（Orange Carotenoid Protein, OCP）是一种可逆光开关（photoswitch），在蓝细菌中发挥光保护作用（Wilson等，2006）。OCP由酮类胡萝卜素色素（keto-carotenoid pigment）功能化；在蓝绿光光子存在下，该色素可诱导构象变化（conformational changes），从而形成能猝灭（quenching）过量吸收光能的光激活状态（photoactivated state）。初步实验首次提供证据表明，OCP晶体脱水（dehydration）会导致预激活状态（pre-activated state）的捕获（trapping）。本实验的核心目标是通过在室温及不同湿度条件下同步采集晶体的衍射（diffraction）和光谱数据（spectroscopic data），验证这一假设。